Wednesday, March 18, 2015

Parabolas are a central topic in high school algebra classes, but, perhaps because of the rigid separation between algebra and geometry classes in the US secondary curriculum, we do not usually treat them as geometric objects. While most teachers are aware of some of the parabola's geometric properties, few of us are familiar with the proofs of those properties.

This last point clashes with the idea that some parabolas are "pointier". My friend and colleague Rachel Chou suggests that it is much easier to see this by shading a finite "cup" on each parabola, and she sent me a Geometer's Sketchpad file to make her point. This led me to revise the final GeoGebra figure on my Geometry of the Parabola page:

I agree: this does help. Go there, read all about it, and download the .gsp file, or the .ggb file.

No comments:

Post a Comment

Search This Blog

Search my Web site

Henri Picciotto

I have retired from the classroom after 42 years as a math teacher in K-12 — from counting to calculus. I now work with teachers and schools, and I continue to develop curriculum.

I share instructional materials on my Math Education Page, and my views on math education on this blog. Also on this blog, announcements about: new pages, updates, etc. on the site; my publications; my appearances at conferences; and my other activities in math education.

--Henri

Note: All material on this blog is copyrighted. You may reproduce it for any non-commercial purpose, as long as you credit me and link to the blog. More info.

Subscribe Via E-Mail

Subscribe in a Reader

#MTBoS

Math Twitter BlogoSphere: network with like-minded educators!

Apologies

All the comments between August 2013 and June 2016 got deleted at once by Google when I disconnected the comments from Google+. I had to disconnect because otherwise it was impossible to remove spam. Apologies to all the commenters.